This invention is concerned with improvements in or relating to extruders, and is especially concerned with extruders of the type including rolls by which material is formed into sheets. Extruders are known in which material to be processed, for example rubber or plastics material, is extruded from a screw-type extruder portion into the nip between two rotating rolls which form the material into a sheet of desired thickness or form. In known extruders an extrusion head is interposed between the end of an extruder screw and the rolls, the extruder head being so shaped that the material issues from a slot parallel with and into the nip between the rolls.
A serious problem encountered with such extruders is to ensure that the material formed by the rolls is withdrawn at the same rate as the material is supplied to the rolls by the extruder. If the material is extruded faster than it is withdrawn, great pressures quickly build-up placing excessive loads on the extruder, the rolls and any connecting members. If the material is withdrawn faster than it is extruded, a non-uniform sheet will be formed. For this reason it has been necessary to construct the various units to withstand high stresses. Certain prior art devices provide means for sensing pressure build-up in the closed passageway and for controlling the extrusion or withdrawing rates. Other devices have provided means for detecting strain or separation of the extruder and roll mounting even though heavily constructed. Such massive construction has made it difficult to separate the units to permit access for cleaning and the like.